Calendar of Physics Talks Vienna

TBA

Speaker:

Christoph Saulder (Uni Wien)

Abstract:

One of the biggest mysteries in cosmology is Dark Energy, which is required to explain the accelerated expansion of the universe within the standard model. But maybe one can explain the observations without introducing new physics, by simply taking one step back and re-examining one of the basic concepts of cosmology, homogeneity. In standard cosmology, it is assumed that the universe is homogeneous, but this is not true at small scales (<200 Mpc). Since general relativity, which is the basis of modern cosmology, is a non-linear theory, one can expect some backreactions in the case of an inhomogeneous matter distribution. Estimates of the magnitude of these backreactions (feedback) range from insignificant to being perfectly able to explain the accelerated expansion of the universe. In the end, the only way to be sure is to test predictions of inhomogeneous cosmological theories. [...]

The coherent scattering through systems with surface roughness is a ubiquitous phenomenon which occurs on
vastly different length and time scales. The effects induced by surface scattering often are the key for the
understanding both of natural phenomena, like the scattering of underwater waves at a rough ocean seabed,
as well as of man‐made devices like optical fibers and waveguides. The understanding of all these systems rests
on a predictive surface scattering theory that relates the properties of a rough surface to the transport
characteristics of the corresponding device and vice versa. Unfortunately conventional surface scattering
theories for the coherent transport through waveguides lack significant ingredients. They do not offer an
analytical connection between the boundary roughness and the transport properties.

The accelerating expansion of the Universe points to a small po- sitive vacuum energy density and negative vacuum pressure. A strong candidate is the cosmological constant in Einstein‘s equa- tions of General Relativity. The vacuum dark energy density ex- tracted from astrophysics is 10^56 times smaller than the value expected from the Higgs potential in Standard Model particle physics and 10^44 times smaller than the contribution expected from QCD condensates. The dark energy scale is however close
to the range of possible values expected for the light neutrino mass. We discuss the cosmological constant puzzle and (new) ideas how to solve it.

Angular momentum and decay distributions in high energy physics: an introduction and use cases for the LHC

Speaker:

Pietro Faccioli (Lisbon)

Abstract:

Measurements of the angular distributions of particle decays give unique insights into the underlying fundamental interactions and play a central role in the determination of coupling properties, in the verification of production models and even in the discovery and identification of new particles.
However, some of the most basic properties of the decay distributions are ignored in the vast majority of the experimental analyses. For example, decades of theoretical and experimental studies used the dilepton decay distributions as crucial instruments (Drell--Yan and quarkonium production, Standard-Model couplings of vector bosons), but only recently some general characteristics of the angular distribution have been systematically addressed, highlighting the importance of the choice of polarization axis, revealing the existence of frame-independent relations and precisely defining

Search for physics beyond the standard model in the Higgs sector with the ATLAS detector

Speaker:

Martin Flechl (Albert-Ludwigs Universität Freiburg)

Abstract:

The discovery of the Higgs boson-like particle at the LHC last year has probably been the most spectacular event in high energy physics in the last thirty years. The big open question now is whether this is yet another boring triumph for the Standard Model or a first exciting step towards new physics. Probing such new physics in the Higgs sector can be done in two ways at the LHC: By finding deviations of the properties of the new particle with respect to the Standard Model expectation; or by finding direct evidence for the existence of additional states compatible with being Higgs bosons. I will review the status of both investigations with the ATLAS experiment: Studies of the properties of the new particle in terms of coupling strength and coupling structure (spin, CP); as well as direct searches for (additional) Higgs bosons, in particular for neutral and charged Higgs bosons.

We show that the basic rule of quantum mechanics establishing connectionbetween the wave function and probabilities can be derived in the framework of classical field theory: random fields interacting with threshold detectors. Moreover, correlated classical random fields (under special assumptions) can reproduce the EPR-Bohm probabilities and hence violate Bell'sinequality. Surprisingly this classical model is not objective. It is contextual: detection/non detection of a "quantum observable" depends on context. This classical (prequantum) field model can be considered as a step towards resolution of wave-particle duality in favor of the purely wave model. In the present model even the second order coherence g^(2)(0) < 1 depending on parameters of the experiment (of the Grangier type: single photon source, beam splitter and detectors in two channels). The parameters of experiment such as detection threshold, "photon duration", photon energy, time window which are typically considered as "technicalities" are elevated to the fundamental level.
[1] A. Khrennikov, Contextual Approach to Quantum Formalism, Springer, 2009